1. Field of the Invention
The present invention relates to methods of fabricating semiconductor devices.
2. Description of the Related Art
In the course of fabricating a semiconductor device, several deposition processes and thermal process are performed. For example, a dielectric layer can be formed through a deposition process that deposits a silicon oxide film or a silicon oxy-nitride film on a substrate. A silicide layer may also be deposited on a substrate in order to reduce contact resistance of a gate electrode. The deposition processes for the dielectric layer and the silicide layer are carried out at a high-temperature.
During deposition of the dielectric layer, a number of Si—H bonds are formed on surfaces of the substrate and a gate dielectric layer. The Si—H bonds can then be destroyed when thermal energy is applied to the substrate during subsequent processes. When negative electric power is applied to a gate electrode on the top of the gate dielectric layer, a hot carrier injection (HCI) phenomenon and/or a negative bias temperature instability (NBTI) phenomenon can occur. The HCI phenomenon can include movement of substrate holes to a gate oxide layer. The NBTI phenomenon can include movement of H+ ions of the Si—H bonds toward the gate electrode. The HCI and NBTT phenomenon may result in a change in the threshold voltage of the associated semiconductor device and may deteriorate its operational characteristics.